Sepsis is a major health care problem with incidence exceeding 750,000 cases a year in the United States alone with an enormous cost to human suffering and national healthcare resources. The basic mechanisms responsible for the high mortality rate of this disease remain unknown but cumulative data points to a key role of early T lymphocyte apoptosis and the subsequent development of a hypo-immune phase in the death of the organism. If the lost T lymphocytes can be replenished the organism may be able to fight the infection and increase the survival rate. The key role of plasma membrane Kv1.3 potassium channels in the activation of T lymphocytes has been recognized for some time. We discovered that this ion channel also present in the mitochondria is a powerful regulator of T lymphocyte apoptosis. We propose to create T lymphocytes rendered relative resistance to apoptosis through inhibition of the mitochondrial Kv1.3 potassium channels and explore adoptive transfer of these genetically engineered T lymphocytes as a novel treatment for sepsis. The working hypothesis is "inhibition of lymphocyte mitochondrial Kv1.3 ion channels prevents apoptosis and adoptive transfer of apoptosis-resistant engineered primary T lymphocytes will enhance survival in sepsis". The three specific aims of the proposal are: Aim 1: Examination of the role of mitochondrial Kv1.3 in T lymphocyte apoptosis, Aim 2: Examination of the mechanisms of mitochondrial Kv1.3 regulation of apoptosis, and Aim 3: In vivo adoptive transfer of engineered primary T lymphocytes and examination of the effect on survival in the murine cecal-ligation-puncture model of sepsis. The innovative hypothesis will be tested using a wide range state-of-art techniques including lentivirus-based ex vivo engineering of primary T lymphocytes, ex vivo and in vitro assessment of apoptosis, organelle-specific expression of various molecular constructs, and the direct biological relevance at the whole animal level examined in a mouse model of sepsis. The emphasis placed on gaining a mechanistic understanding of the role of mitochondrial Kv1.3 in the regulation of apoptosis distinguishes this proposal from a purely pre-clinical phenomenological research. The research team, along with the consultants, comprises a unique collection of expertise necessary to execute this multi-faceted project.